1. Field of the Invention
This invention relates to a motion-adaptive device for separating a luminance signal and a color signal in color video systems such as color television receivers. Such a signal separation device is generally called a Y-signal/C-signal separation filter.
2. Description of the Prior Art
Color television receivers include a filtering device for separately deriving a luminance signal (Y signal) and a color signal (carrier chrominance signal, C signal) from a composite color television signal.
Typical motion-adaptive Y/C signal separation devices include two filters each for separating a luminance signal and a color signal, the first filter being responsive to a correlation between lines in a common picture and the second filter being responsive to a correlation between frames. One of the two filters is selected in accordance with an output signal from a motion detector sensing motion of pictures.
Japanese published unexamined patent application No. 61-274493 discloses a digital decoder which includes a Y/C signal separation circuit responsive to a variation in a common picture, a Y/C signal separation circuit responsive to motion of pictures, and a band pass filter. Output signals from the two separation circuits and the band pass filer are mixed in accordance with spatial variations and time-dependent variations in pictures to separately derive a final luminance signal and a final color signal.
The 1987 National Convention Record of the Institute of Television Engineers of Japan includes a paper titled "Motion Detector Using NTSC Two-Frame Difference and Spatio-Temporal Accumulation" in which time and space are expanded in relation to the detection of motion of pictures in order to improve the accuracy of the motion detection.